Actuators are commonly used in many industries for all types of applications to move system components in a desirable manner. Depending on the particular implementation, any number and type of actuators may be used. Some applications, such as actuation in aircraft flight control systems, require a motor drive having high acceleration and high holding torque properties. These characteristics, however, provide a difficult hurdle given that the desire for high acceleration characteristics results in a motor utilizing a low inertia rotor, which in turn hinders torque production. To deal with this issue, conventional solutions rely on a heavier motor with a higher power rating, sized to satisfy the required acceleration and torque parameters. However, in the aircraft industry, the size and weight of all aircraft system components are a primary concern.
Permanent magnet motors can be beneficial for use for actuation applications. With conventional permanent magnet motors, a permanent magnet array may be secured to a rotor shaft and allowed to rotate within the magnetic fields produced by surrounding stator windings. The appropriate manipulation of the current through the stator windings produces the desired forces on the permanent magnet array, creating corresponding rotation of the rotor shaft. The permanent magnet array is commonly arranged with the magnetic poles of the permanent magnets having a radial magnetic flux configuration with respect to the rotor shaft. The rotor shaft is typically manufactured as a solid piece of magnetic material, or back iron, that accommodates the magnetic flux from the permanent magnets mounted around the shaft.
One problem with this type of conventional configuration relates to the magnetic flux penetrating the rotor shaft, and the corresponding back iron. During operation of the motor, the high-speed rotation of the rotor creates substantial eddy currents. Because of the large quantity of magnetic flux penetrating the back iron and the corresponding eddy currents during operation, the rotor shaft experiences significant heating, which could result in premature failure and could require additional cooling systems depending on the application. Additional cooling systems increase the cost and weight of the system, as well as adding to the complexity of the overall motor system and the corresponding maintenance requirements.
It is with respect to these considerations and others that the disclosure made herein is presented.